Willy Brandt, then Chancellor of West Germany, falls to his knees at the memorial to the Warsaw Ghetto in 1970: This spontaneous gesture was the most powerful and moving image of German repentance of the whole postwar era

First: why an open letter? I have never written one before, whereas you have written dozens. You are, so to speak, Europe’s leading man of open letters. I admit that the idea of turning the tables on you did appeal to me.

But there is another, more personal reason for my decision to address you in this way. In a newspaper interview about your autobiography, Peeling the Onion, you have admitted, after 60 years, that you belonged to the Waffen SS. I want to make you aware of my feeling of betrayal —a feeling I believe I share with most of your countrymen. And I want to show solidarity with the victims, living and dead, of the regime you tried so hard to prolong.

A public intellectual like yourself is, of course, entitled to preserve a private sphere. But there are certain biographical facts about which it is necessary to be open, as I am sure you would agree. You do not need me to tell you that, for a German of your generation, frankness about your activities during the Third Reich is not merely a moral imperative, but a sine qua non for any kind of public role.

Let me first recall a memorable scene in 1970: Willy Brandt falling on his knees at the memorial to the Warsaw Ghetto. It was the most moving and powerful image of German repentance of the whole postwar era. You were there at his side, representing German culture, as the German Chancellor went to sign his historic treaty with Poland and made his spontaneous gesture of atonement for the Holocaust.

Afterward, you wrote to thank Brandt effusively for the privilege of “being allowed to be moved”. What strikes me now is the artificiality, not only of the language but also the emotion. For how could a man living a lie respond adequately on such an occasion?

You were his friend and ally; you campaigned for him. What would this great German statesman, an émigré who risked his life for the anti-Nazi resistance, have said if he had known about your past and your deceit? Would he have tolerated your presence? He is dead, but we know how a great Polish leader, Lech Walesa, feels about you. He says that Gdansk, your native Danzig, would never have given you the freedom of the city if the Poles had known about your past. Do you not see the damage you have done to Germany’s good name?

Another memorable scene: Bitburg cemetery in 1985. President Reagan and Chancellor Kohl commemorated the 40th anniversary of the end of the war, at the height of anti-American agitation. In the snow-covered military cemetery, graves of Waffen SS soldiers were discovered. Americans were scandalised, Germans embarrassed, but the ceremony went ahead.

You joined in the denunciation of Reagan and Kohl for appearing to pay tribute to the dead of the SS. Somehow, though, it didn’t occur to you to say that you could easily have been one of them.

Do I need to remind you of the many public figures who have been disgraced over the discovery of a disreputable past? Do you recall Germany’s best-loved chat show host, Werner Hofer? Aged 74, he was ignominiously sacked after it emerged that he had written Nazi propaganda during the war.

Or perhaps you heard the great opera singer, the late Elizabeth Schwarzkopf? She kept her Nazi activities quiet until after she retired, and she took to the grave the secret of which senior Nazi’s casting couch launched her career.

But the most celebrated case was, of course, Kurt Waldheim. As a staff officer in the Balkans he was a small cog in the Nazi war machine that was committing terrible crimes there — and yet as UN Secretary General he conveniently omitted to mention any details about his wartime record.

Waldheim’s silence changed the history of Austria, for better and worse. But the curious thing was — as I discovered when I interviewed him in the Hofburg Palace — that he refused to believe that he had done anything wrong. He never apologised, never explained. Nor, by the way, have you.

Despite this, it must be difficult for you to see anything in common between Waldheim’s case and your own. What has an ambitious bureaucrat, an unscrupulous mediocrity like him to do with a great writer like you? Let me tell you: Waldheim was a classic example of a phenomenon, which Nazi Germany created and for which the German language promptly created the perfect expression: der Schreibtischtäter, the “desk criminal”.

You relished using that neologism back in the 1960s, denouncing the conservative government of Konrad Adenauer for its Atlanticism, its Cold War rhetoric, its eagerness to rearm and join Nato, because Adenauer, though his own record was impeccable — he had been sacked as Mayor of Cologne and later imprisoned by the Nazis — did not scruple to promote former Nazis whom he found useful.

There was Hans Globke, who had written a legal commentary on the anti-Semitic Nuremberg laws, and became the Chancellor’s right-hand man. There was General Gehlen, the intelligence chief, who did not mind whether he spied for Hitler or Adenauer. And there was Kurt-Georg Kiesinger, who had merely been a Nazi Party member throughout the Third Reich, an ordinary opportunist, but who later rose to become Chancellor of West Germany.

That was a scandal in your eyes, and in one of your open letters you called on him to resign — for the crime of having been a Nazi. You never let the German Right forget its shady past for one second. But you must have prayed that nobody remembered your own.

Oh yes, you made the most of your moral superiority over those Schreibtischtäter. You pissed on them from a very great height indeed. Except that it now seems that you were one of them. You were a desk criminal, too, only your crimes were committed in the front line and concealed at the desk for the next six decades.

You spent your life signing books, not death warrants. But you were in a different league of culpability from the Kiesingers and Globkes and Waldheims. You, unlike them, were a member of the Waffen SS. The Waffen SS was declared a criminal organisation by the Nuremberg tribunal just after the war.

You knew this, I assume, because you have often said that you were one of the millions of Germans who did not believe the Holocaust could have been perpetrated by the nation of Goethe, until you were convinced by the evidence at the Nuremberg trials.

You were fortunate to escape retribution at the time, and even more fortunate to have done so for 60 years. Why did you finally come clean? You say yourself: “It had to come out.” But why? Were there incriminating documents? Had you confided in your family or friends? Was some young historian finally on your trail? Or did your conscience prompt you to come clean before you died — better late than never? I should like to think so.

But the absence of contrition — indeed, of any self-awareness beyond self-justification — in your interview excludes that possibility. I am afraid that the most cynical motive is also the most plausible: you had an autobiography to sell. The media spectacle, the national soul-searching that you must have known would be unleashed, had one overriding purpose: to make sure that your latest — very possibly your last — book would be a bestseller.

There is a studied vagueness about your references to your past, but about one thing you were quite clear: you were not personally responsible for the Nazi crimes. In your speech “Writing After Auschwitz”, given 16 years ago, for instance, you recall the young poets of the 1950s: “All of us were aware, some clearly, some vaguely, that we belonged to the Auschwitz generation — not as criminals, to be sure, but in the camp of the criminals.”

Even more tellingly, in a speech you gave before Israeli audiences in 1967, you stated: “You can tell by the date of my birth that I was too young to have been a Nazi but old enough to have been moulded by [the Nazi] system . . . The man who is speaking to you, then, is neither a proven anti-fascist nor an ex-National Socialist, but rather the accidental product of a crop of young men who were either born too early or infected too late. Innocent through no merit of my own, I became part of a postwar period that was never to be a period of real peace.”

How ingeniously you deflected the suspicions of your listeners, many of whom must have been Holocaust survivors, by disclaiming any pretence of opposition. You were merely innocent through no merit of your own. In what sense innocent? Too young to have been a Nazi party member, but not too young to have volunteered at age 15 to fight for Hitler’s Reich!

You tell us that you did not ask to join the Waffen SS, but rather the U-boats — whose recruits were also notoriously hardline Nazis, by the way. The historian Joachim Fest does not believe this story, and neither do I. (He says he would not buy a used car from you now, and who can blame him?)

By the time you volunteered in 1943, it was clear to all but those blinded by ideology that Germany was losing the war. By joining up in the Waffen SS, you were joining the Nazi elite, a band of bloody brothers who believed they were destined to rule Europe. They did not take just anyone.

You tell us in your interview that you wrote your first, unpublished novel around this time, now conveniently lost. It was set in the idealised medieval world of Teutonic knights that, as you omit to mention, was a favourite of Goebbels’s propaganda films. You never finished it, you tell us, because after the first chapter all the characters were dead.

You make light of it, but it is further proof that you, along with many German teenagers, were steeped in the Nazi death cult. You and your comrades were careless of how many people you killed, for to you they were scarcely human. Your mentality was not unlike that of the Islamist suicide bombers of today.

The last photograph of Hitler shows him decorating lads like you. All the evidence points to you having been not only a fanatical Nazi but a dangerous one too, eager to wear the death’s head insignia of the SS.

The truth that now emerges, Mr Grass, is that you were one of the last-ditch defenders of the Third Reich. You were a soldier in the 10th SS Panzer Division Frundsberg. Let us be clear: the Waffen SS did not run the death camps, but its troops — some 900,000 of them by the end —were deeply implicated in the Holocaust and responsible for many of the worst atrocities of the war.

We await with interest your account of your own part in these war crimes, but your memoirs will be treated by historians with suspicion, as no more reliable than those of other SS men — Adolf Eichmann’s, for instance, which he wrote while awaiting his trial and execution.

No doubt the comparison shocks you. But Eichmann, like you, was an imposter. He, too, reinvented himself after the war rather than face up to his past. True: he was a senior officer, responsible for rounding up millions of Jews to be sent to death camps, while you were a young soldier. But you both tried to exculpate yourselves by pleading that you were only obeying orders.

The most striking difference is that he was found out 45 years ago, and paid for his crimes with his life. You got away with it.

What we do know is that your panzer division saw action on both the Eastern and Western fronts in 1944-45, notably during the Allied airborne landings at Arnhem. Your bitter, bloody and ruthless resistance there and elsewhere postponed Germany’s inevitable defeat. While you were making your heroic last stand, Jews and other helpless “enemies of the Reich” were still being murdered in the camps and, later, on the death marches — thousands of them every day.

In the last weeks of the war, you were wounded in a battle near Cottbus. Apparently your unit was under orders to rescue Adolf Hitler from the bunker in Berlin, in order to let him complete his self-appointed mission to exterminate the European Jews. As it turned out, Hitler preferred to die by his own hand in Berlin.

At the time, did you regret your failure to rescue the Führer to whom you had solemnly sworn allegiance? You, once considered the greatest postwar German writer, nearly died trying to save Hitler!

Unlike most of your comrades, you survived. Even after his death, you and your comrades were to continue the war as terrorist “werewolves”. But you were hospitalised and managed to surrender to the Americans. You spent a year in a prisoner-of-war camp — far less than many of your comrades. After your release, you were able to reinvent yourself.

Thereafter you kept silent about your part in the greatest crime in history for more than 60 years. You kept silent about your past when other intellectuals were discredited for membership in the same Waffen SS.

You kept silent about your past when debates raged about whether Germans were collectively guilty, about whether the Nazi genocide was unique, about the appropriate way to commemorate the war and the Holocaust.

What makes most Germans feel betrayed is not the fact that you were a member of the Waffen SS, a criminal organisation, but that you made the fateful decision not to share with anybody the most important single fact about yourself.

Not with your fellow writers in the Gruppe 47, most of whom were, like you, war veterans, who gave you your first breaks; not with the publishers and the book trade that marketed you as the voice of a new, untainted but angry young generation, and above all not with the reading public, which has remained true to you since you broke on to the literary scene in 1959 with your first novel, The Tin Drum.

It was, and is, a modern classic. It was followed in quick succession by two more war novels, Cat and Mouse and Dog Years. Over the years you have returned again and again to the war years for inspiration. Four years ago you published Crabwalk, your fictionalised depiction of the tragic sinking of the liner Wilhelm Gustloff, laden with German refugees fleeing the Russians in the last days of the war — a subject dear to the hearts of old Nazis that, had you not been a life-long leftist, would have cast doubt on where your true sympathies lay. But you did not vouchsafe your readers that essential detail about what you were doing at the time.

Throughout your fiction there are characters in denial, whose bad faith or failure to come clean have terrible consequences. From the first, you invested “the power of silence” with supernatural force. Variations on the theme are repeated over and over again in your work. You urged Germans to break their unhealthy silence about the Holocaust, the “inability to mourn” in the catchphrase of the day. But you did not follow your own advice.

I have before me two of your books. The first, a translation of your speeches and, yes, open letters, is entitled Speak Out! Published in 1968, it is introduced by Michael Harrington, a leading American liberal, who praises you for your outspoken courage as a public intellectual. The ironies here are too obvious.

Granted: you are not the inmate of a mental hospital. Unlike Oskar Mazerath, the diminutive hero of The Tin Drum, you do not play the drum incessantly nor utter shrieks so high-pitched they shatter glass. Oskar, your brainchild, disguises himself as a retarded infant with a mental age of three in order to bear witness to the sinister events around him, Germany’s descent into the abyss of the Third Reich.

Oskar’s unbearable scream is a protest, all the more eloquent for being inarticulate, against that silence in the face of depravity that made Hitler possible. In Oskar, you created one of our most memorable metaphors for the moral insanity of Nazism.

Now, however, you have forced us to read your books again, and in an ambiguous light. In your interview last weekend, you sought to justify your decision to volunteer as a teenage revolt against the narrow confines of your petty bourgeois home. To thus romanticise your youthful Nazi allegiance is, frankly, sickening, but maybe that is how you saw it at the time.

If so, The Tin Drum may not be the novel we thought it was. Your harsh social satire is aimed at the people you grew up with, small shopkeepers with a bust of Hitler beside that of Beethoven. In real life, however, your bid for freedom was not directed against the Nazis, but for a more radical version of the ideology: the death or glory paganism of the Waffen SS.

Would the book have been read as it was, would it have won you the Nobel Prize, would Volker Schlöndorff have made it into a no less remarkable movie, if your background had been known?

But you are not a literary character. You are a writer: the most celebrated in Germany, perhaps even in Europe, and winner of every imaginable literary award, including the Nobel Prize.

For nearly half a century you have been recognised by your country’s citizens as a moral arbiter, even (absurdly) as the conscience of Germany. In that capacity, you have sat in judgment on your fellow Germans, as indeed on America and just about everybody else.

Like your American counterpart Noam Chomsky, like countless writers and intellectuals of the Left from Gabriel García Márquez to Harold Pinter, you have worked hard to discredit the political and economic system to which you owed your success: capitalism. You did your best over many years to undermine the Atlantic alliance — the same alliance, incidentally, that liberated Europe from the tyranny of your countrymen.

During the Cold War, and now in the war against Islamist terror, you have frequently made use of your hard-won liberty to make common cause with its enemies. You joined in the mythologising of the Baader-Meinhof terrorist movement. You are a supporter of the European ideal, but only as a counterweight to America. You were delighted when Chancellor Schröder broke with President Bush over the Iraq issue, and legitimised the tide of anti-Americanism that then swept Germany.

Soon after the liberation of Iraq, I was told by one of your fellow writers that you were so angry with Tony Blair and George Bush that you were boycotting Britain and America. You probably won’t know Aurel Kolnai’s book The War Against the West, a study of Nazism published in 1938. But its title sums up Hitler’s struggle.

Now that we know how you began your career, with a thorough indoctrination in the Waffen SS, your lifelong loathing of the West takes on a new and sinister significance.

You have always presumed to occupy the moral high ground, condemning the elected leaders of the West on the somewhat dubious authority that Germans have traditionally accorded to intellectuals. I say dubious, because you know as well as anyone how that authority has been abused in the past.

Heaven knows, you had enough fun at the expense of Martin Heidegger in Dog Years, mercilessly satirising his “jargon of authenticity”, his existential angst and phoney pathos, his pseudo profundities and oracular orotundities. You know as well as I do how deeply the Nazi bacillus took root in German culture, and how the gullible Germans, stylising themselves as the nation of Dichter und Denker, of poets and philosophers, let themselves be manipulated by fanatics and fiends.

You didn’t only lecture Nazi intellectuals, either. One of your many open letters reprimanded the East German writer Anna Seghers for lending her authority to the Berlin Wall in 1961. By the time the Wall came down in 1989, you seemed to have had a change of heart. You embarked on a quixotic campaign to persuade Germans that they would really be better off living in two states.

The only people who agreed with you were the old Communist intellectuals who had done well out of the division of Germany. Yet even they, apologists for a totalitarian regime in which they no longer believed, were not as disingenuous as you.

It was part of your disguise to adopt as a badge of honour the old anti-Semitic insult “rootless cosmopolitan”. Your friend Stefan Heym, Communist time-server that he was, was the genuine article. As a Jew, he had been driven out of Germany in 1933, and returned in 1945 as an intelligence officer in the US Army. He might even have interrogated you. Luckily for you, he did not. The East Germans would have had no hesitation in blackening your name, despite the fact that your anti-Americanism and your lifelong campaign to detach West Germany from Nato were quite useful to them.

Why did you lie? For your 60-year silence was a lie, an unspoken reproach that forced you to lie again every time you sat down to write. Perhaps you no longer know why you did it. I have a theory, which may be mistaken, but which takes us back to your own “zero hour” at the end of the war.

When you started your life again after your release from PoW camp, you decided to be an artist. That was your first love, and you were talented. You have never ceased to draw and print. Your collected graphic art, In Kupfer, auf Stein (In Copper, on Stone), documents an impressive body of work. But you were not content to be a humble printmaker. You wanted to be a great writer.

In literature, unlike art, you were a late developer. You did not get your first poem published until you were 28, and you were 32 by the time your first novel appeared. But you were determined to make your name as a writer. It was only when you became a literary celebrity that your secret became a huge liability. If you had grasped the nettle then, your new career, which meant so much to you, might have been stillborn. You chose silence.

And so you made your pen your accomplice, in one of the shabbiest deceits ever practised on a reading public — a German public that desperately needed you to be the person you presented yourself as. In the annals of European literature, I cannot recall a similar case. Literary hoaxes, even those in which the author has pretended to be an eyewitness to the Holocaust, are innocent by comparison.

You are often compared to Thomas Mann, but you are no more a Mann than you are a man. The only Mann character with whom you have much in common is Felix Krull, the confidence trickster. Your rise and fall recalls the greatest of all German myths, that of Faust, which Mann explicitly connected with Nazism.

Your fate, though, is not tragic, but comic. Your reputation, which was already in decline, now lies in ruins. It is no consolation that you may acquire a new following among the Germans you most affected to despise, those who think the Waffen SS has been much misunderstood.

I saw you once. I have only a dim memory of it, because it was well over 30 years ago, when I was a schoolboy of about the age at which you volunteered. You came to give a reading in London, together with two other German writers: your friend the novelist Siegfried Lenz and the East German poet Peter Huchel.

The other two were men of integrity, neither of whom concealed his conduct in the Third Reich. But you were the star turn, reading from your play about Brecht’s role in the 1953 workers’ revolt in East Berlin, The Plebians Rehearse the Uprising. You were sympathetic to Brecht and his grubby compromises — praising Stalin and Ulbricht in public, writing bitter verses in private (“Would it not be easier for the government/To dissolve the people/And elect another?”).

I should have seen then and there what kind of man you were. I remember warming to Huchel, by then a broken, disillusioned figure living in exile and waiting to die. But my German teacher had eyes only for you: the hero of the West German Left, the very model of a modern intellectual. I suppose I was impressed, too. I subsequently devoted much of my life to writing about German politics, history, and culture. You touched my life, as you touched countless others.

What, though, if we had known you for what you really were? Now that we do know your secret, the least most people might expect would be an act of contrition. But I, for one, do not expect it from you. You are not sorry, neither for what you did nor for what you did not do.

To apologise now would merely compound your insincerity. We want no more pilgrimages to Auschwitz. No, Mr Grass, it is too late for that. You have lived and will die a fraud, a coward, and a hypocrite. One day you may be forgotten, but you will never be forgiven.

As I suspected, the East German Communist secret police, the Stasi, knew all about your Waffen SS membership. The truth would have come out anyway when your Stasi file is published next year. Your decision to keep quiet actually exposed you to blackmail by the Stasi. It seems that the facts were also contained in American military archives. Your file might have surfaced at any time over the past 60 years, if anybody had cared to look.

I see, too, that your publishers are rushing out your memoirs early, to cash in on the worldwide publicity generated by your admission. They have also released brief extracts to tempt us. They disclose that you remained an unrepentant anti-Semite even after the war.

While working as a prisoner of war in the kitchens at a US air base, you found yourself — almost certainly for the first time in your life — having to treat Jews as equals. Your co-workers were Jewish refugees, recently released from German concentration camps, who must have endured unimaginable suffering and humiliation at the hands of your comrades in the SS.

Not surprisingly, when a row broke out in the kitchen, they shouted: “Nazis, you Nazis!” Well, that was no more than the truth. You admit that you were proud to serve in the Waffen SS. So how did you respond? “We retorted: ‘Just go away to Palestine!'”

For you, it seems, the war wasn’t over. You still wanted a Europe, and especially a Germany, that was Judenrein, ethnically cleansed of Jews. Given your hostility to Israel today, some 60 years later, we are entitled to ask whether your “denazification” went far enough.

From what we have seen of your memoirs, I do not expect to learn much from them. The extracts so far published do not explain the mystery of your silence. “I kept silent about it after the war out of a growing shame,” you write. You still do not seem to understand that your silence was itself shameful.

Now that you are under intense though belated scrutiny, you are full of self-pity and self-justification. On German TV on Thursday night, you complained: “What I am experiencing is an attempt to make me a persona non grata, to cast doubt on everything I did in my life after that.”

The German Genius: Europe’s Third Renaissance, the Second Scientific Revolution and the Twentieth Century by Peter Watson; Fame by Daniel Kehlmann; The Box by Günter Grass; and Portrait of the Mother as a Young Woman by Friedrich Christian Delius